Near-space technologies are gaining significance due to their potential applications in research, surveillance, communications and remote sensing. Space startups like Virgin Galactic, Blue Origin and SpaceX are already making waves by outlining plans to deliver various forms of commercial space flights in near space. ‘Falcon 9’ reusable rocket boosters belonging to SpaceX have successfully recovered on drone ships/the land/launch pad. In February 2023, a United States Air Force fighter jet shot down a Chinese spy balloon over the coast of South Carolina. The Chinese Near Space Flight Vehicles (NSFV) program is in the spotlight since the PLA plans to commission a ‘Near Space Command’. China has also made advancements in hypersonic glide vehicles capable of evading leading missile defence systems across the globe.
Introduction
Near-space technologies refer to the development of systems, devices and platforms designed to operate in the region of Earth’s atmosphere that lies between 20 km and 100 km. This area is above the range of conventional aircraft but below the altitude at which satellites typically orbit. Platforms used are high-altitude balloons, hypersonic glide vehicles/weapons, high altitude long endurance unmanned aerial vehicles (UAVs), reusable rocket boosters and small satellites. Being economical and easy to develop, this sphere is certainly a favourite for space startups and academia.
Some of the key applications of near-space technologies are telecommunications and environmental monitoring, evaluating natural disasters and remote sensing using high-resolution radars and optical sensors. They can be used to collect data for a variety of applications such as agriculture, forestry and urban planning. Military applications encompass surveillance of enemy territories, reconnaissance, target acquisition and tracking. These technologies are very effective in extending operations over the horizon (OTH). Near Space Labs, Google Loon (Alphabet), Northrop Grumman, SpaceX and NASA are actively involved in developing and innovating near-space technologies. This article tries to explore the possibilities of near-space technologies for applications in civil and military domains.
Host of Advantages
Deploying platforms in near space is much cheaper than launching satellites. These platforms can be relocated or navigated more easily than satellites. They can also be programmed to remain over a location for extended periods, unlike satellites that orbit around the Earth. Near-space instruments can collect real-time data at high resolutions, valuable for climate studies, disaster monitoring and environmental research. Reusable low-cost systems being developed are making near-space endeavours are more sustainable.
High-Altitude Pseudo-Satellites (HAPS)
These are unmanned aircraft or airships designed to operate at near-space altitudes for long periods. High Altitude Pseudo Satellites (HAPS) are solar-powered unmanned aerial vehicles (UAVs) that operate in the stratosphere at altitudes between 18 km and 25 km. They can provide services similar to artificial satellites and can hover for extended periods, potentially months or years, by generating solar energy. HAPS are nearly stealthy and are very effective for military surveillance and can track enemy movements at high altitudes over large areas. The capacity of energy sources and battery technology plays a major role in the endurance of HAPS.
Airbus ‘Zephyr S’, a solar-powered very-high-altitude unmanned aircraft is in the midst of a long-duration test flight and has already been aloft for 17 days so far. A similar craft Qimingxing 50 is currently under development in China.
The CSIR-National Aerospace Laboratories (NAL) in India has tested a prototype HAPS capable of hovering for hours and aims to develop a larger version with extended flight capabilities by 2027. Companies like Airbus are leading the development of HAPS platforms like the Zephyr, which has set records for endurance and altitude, demonstrating the potential of these vehicles in practical applications.
Hypersonic Glide Vehicles
Hypersonic glide vehicles (HGVs) are advanced military systems that travel at speeds exceeding Mach 5 and have the capability to manoeuvre during flight. This “boost-glide” mechanism allows them to evade missile defence systems by altering their flight path/trajectories in the near space region after making a re-entry from space. Since the glide path can be altered during travel, it is very difficult for any missile defence system to predict the future position or trajectory of the approaching glide missile/ vehicle. With a speed exceeding 10 Mach, it becomes impossible to neutralise these missiles/vehicles after the launch.
Both China and Russia have conducted numerous successful tests of hypersonic weapons. China’s hypersonic arsenal includes the missile DF-17, a medium-range ballistic missile with a hypersonic glide vehicle that has a range of 1,600 km whereas the missile DF-41 intercontinental ballistic missile ranges more than 12000 km. Hypersonic technology demonstrator vehicle (HSTDV) being developed by DRDO is an unmanned scramjet demonstration aircraft for hypersonic speed flight and acts as a carrier vehicle for hypersonic and long-range cruise missiles. HTNP Industries Pvt Ltd, an Indian deep-tech startup is also developing a hypersonic boost glide vehicle HGV-202F.
Reusable Rocket Boosters
Reusable rockets are designed to be refurbished and flown multiple times, significantly reducing the cost of access to space. The Falcon 9 rocket’s first stage separates at an altitude of approximately 70 to 80 kilometres during the ascent traveling at 10 Mach speed. After separation, the first stage can reach an apogee (the highest point in its trajectory) of around 100 kilometres due to its remaining inertia and then descend back to earth for safe recovery. The re-entry burn of the Falcon 9 booster occurs as the rocket descends into near space at around 60 kilometres altitude, allowing it to reduce speed before entering the denser parts of the atmosphere. This technology significantly reduces the cost of space travel and facilitates a reusable and sustainable solution.
Space Zone India is an aero-technology company in Chennai that aims to provide low-cost, long-term solution ‘RHUMI’ in the space industry under the leadership of Mr Anand Megalingam, mentored by India’s Moon man, Dr Mylswamy Annadurai Former Director of ISRO Satellite Centre (ISAC). RHUMI 1 Rocket is equipped with a generic-fuel-based hybrid motor and electrically triggered parachute deployer, RHUMI is 100% pyrotechnic-free and 0% TNT. On August 24, 2024, this rocket carried 3 Cube Satellites and 50 PICO satellites into a suborbital trajectory using a mobile launcher and later recovered at 1.8 kilometres from the coastline near Chennai post successful descent.
High-Altitude Balloons (HABs)
These are lighter-than-air balloons, typically filled with helium, used for scientific experiments, weather monitoring, and communications. They can carry sensors and communication equipment to near-space altitudes. They are lighter-than-air balloons designed to operate at altitudes in the stratosphere, typically between 18 km and 37 km. These balloons are used in a wide variety of applications, from scientific research and weather monitoring to communication and even space exploration. HABs offer a cost-effective way to reach near-space altitudes upto 50 km for extended periods, making them highly valuable for missions that require high-altitude observations or testing.
The balloon itself is made from materials like latex, polyethene or other lightweight, durable fabrics. The balloon needs to be both flexible and strong enough to withstand low pressure, extreme cold, and radiation in the upper atmosphere. HABs are typically filled with lighter-than-air gases such as helium or hydrogen. Helium is more common due to safety concerns with hydrogen’s flammability. Below the balloon, a payload capsule is suspended. HABSs can be designed and constructed for flights that can last several weeks. While some balloons burst after reaching their maximum altitude, others are designed to slowly descend or remain at specific altitudes for extended durations.
HAB Payloads and Navigation
HABs can carry various scientific instruments to study cosmic rays, the upper atmosphere and space weather. Cameras, sensors, and detectors are common payloads for research and data collection. Some HABs are used for communications purposes, acting as temporary relay stations for mobile networks, internet, or broadcasting services. Instruments can be used to measure atmospheric pressure, temperature, humidity, ozone levels, and pollution, contributing to climate studies and meteorological research. Military HABs carry small radars and signal-snooping sensors at stratospheric altitudes, which could provide strategic advantages over adversaries by even disrupting enemy operations and sensors.
High-altitude balloons are typically navigated using electronic equipment such as GPS receivers, alongside other technologies like radio transmitters and cameras to assist in tracking and coordination. The ascent and manoeuvring of these balloons can also be optimized through careful planning and the use of lighter-than-air gases to ensure they reach desired altitudes and directions.
Near Space Applications
Near-Space Communications: Platforms in near space, such as balloons or drones, can act as relay stations for telecommunications or internet services. This is particularly useful in remote areas or during disasters when ground-based infrastructure is unavailable. NASA’s Near Space Network (NSN) provides critical communication and navigation services for missions operating within one million miles of Earth. This network supports numerous missions by facilitating data transmission between spacecraft and ground stations.
5G Deployment and Broad Band Communications: Companies are using near-space technologies to enhance global connectivity by providing a middle ground between terrestrial 5G networks and satellite communications. How this technology can be used to supplement satellite broadband like spaceX can for last-mile connectivity can be explored.
Environmental Monitoring and Remote Sensing: High-altitude platforms can carry sensors to monitor atmospheric conditions, pollution, ocean surface and even wildlife. They can capture high-resolution images and gather data over large geographic areas. Real-time data collection can aid in assessing damage from natural disasters and coordinating response efforts. land use, vegetation health, and urban development. Near Space Labs specializes in high-resolution geospatial imagery has high-altitude balloons known as “Swiftys” that can reach altitudes of 60,000 to 85,000 feet and provide imagery with a resolution of 10 cm per pixel and can cover large areas of up to 1,000 square kilometres in a single flight and operate on a zero-emission basis, making them environmentally friendly compared to traditional aircraft.
Scientific Research: Near space is an ideal environment for scientific experiments, particularly in areas like astronomy, atmospheric physics, and meteorology. High-altitude balloons can detect cosmic rays from space without interference from the dense lower atmosphere. Observing the stars from near space allows scientists to avoid much of the atmospheric distortion that affects ground-based telescopes.
Military Applications: Near-space platforms can be used for surveillance and intelligence gathering. They offer a cheaper and potentially more flexible alternative to satellites, being closer to Earth and able to stay over a specific location for longer periods. Hypersonic weapons with bizarre glide paths in the near space are difficult to detect and neutralise. China has developed the Near Space Flight Vehicles (NSFVs) to enhance battlefield situational awareness and improve communication among dispersed forces. China’s NSFVs include a range of platforms from balloons to UAVs, which are increasingly seen as vital for intelligence, surveillance, and reconnaissance (ISR) operations.
Launch Platforms for Satellites and Rockets: Near-space platforms can be used as a launch point for small satellites or suborbital rockets. This can reduce the energy needed for a rocket to reach orbit, making space access cheaper and more efficient. ‘NearSpace Launch’, a company focused on providing reliable satellite connections through commercial networks offers payload launch services for small satellites into orbit.
Space Tourism: Several space startup companies are developing stratospheric tourism experiences for recreational purposes. Virgin Galactic, SpaceX, Blue Origin, Orion Span and Boeing are the leading ones. ISRO is working on a reusable space tourism module expected to be operational by 2030. Reusable technologies would ensure sustainable and low-cost near-space endeavours in the coming years. World View Enterprises plans to send passengers in capsules attached to high-altitude balloons to experience the curvature of the Earth and near-space conditions without reaching orbital space.
Challenges and Limitations
Sustaining flight at near space altitudes requires efficient energy sources. Solar-powered HAPs are a potential solution, but maintaining power for long durations remains a challenge. Extreme conditions in near space including very low temperatures, strong winds and ultraviolet radiation are to be considered at the design stage. Near-space platforms operate in airspace that is not heavily regulated and hence managing them in airspace may become difficult. The scientific community and space agencies are focused on deep space exploration and are currently ignoring the possibilities in near space.
Conclusion
Near-space technologies represent an exciting frontier between aviation and space, with applications in communications, science, defence and even tourism. They serve as a complement to both satellite and terrestrial technologies and provide a cost-effective, flexible approach to accessing the stratosphere and lower mesosphere. The majority of the near-space technology elements are being designed as reusable and have a lower carbon footprint. Since ISRO has started focusing on long-endurance deep space missions with larger platforms, creating a new agency to develop near-space technologies can be deliberated. Space startups can complement ISRO in near-space innovations since the initial investments are less compared to deep space technologies.
Disclaimer: The views and opinions expressed by the author do not necessarily reflect the views of the Government of India and Defence Research and Studies
Title image courtesy: NASA
